The present disclosure relates to a light quantity measurement apparatus that measures the quantity of light of various colors in a time-division color display projector light source, and to a projection-type display device equipped with this apparatus.
Patent Literature 1 (Japanese Laid-Open Patent Application 2012-53279) discloses a color image formation device that allows good gradation expression corresponding to changes in the light quantity of a light source.
This color image formation device comprises an image input terminal to which an image signal is inputted, an image data converter for producing an image signal that is converted on the basis of a gradation conversion table, with respect to an image signal inputted from the image input terminal, a sensor for measuring the light quantity of various light source devices, and a gradation conversion table update section for measuring the light quantity with the sensor both just after the light source devices are turned on and just before they are turned off by an emission controller, and updating the gradation conversion table.
Thus, with the light source device disclosed in the above-mentioned publication, a sensor that measures the light quantity of various light source devices is used to measure the light quantity immediately after the light is turned on and immediately before it is turned off, and a digital signal that has undergone A/D conversion is corrected by using gain.
Consequently, good gradation expression can be obtained even if there are individual differences between devices, changes in the environment, changes over time, etc.
However, with the light quantity measurement apparatus disclosed in the above-mentioned publication, the light quantity of a plurality of colors of light emitted from the light source of a time-division color display projector is measured using a single photosensor. When a single photosensor is thus used to measure the light quantity of a plurality of colors of light, there is a large difference in the measurement sensitivity for red, green, and blue, so measurement accuracy ends up decreasing.
Furthermore, there is generally a difference in the projection energy of a plurality of colors of light because the colors are balanced so that the desired white will be achieved with three colors, such as red, green, and blue.
This disclosure provides a light quantity measurement apparatus with which measurement accuracy can be improved by controlling the measurement sensitivity for red, green, and blue, even when the light quantity of a plurality of colors of light (that are emitted from a light source and have different energies) are measured with a single photosensor, as well as a projection-type display device equipped with this apparatus.